如何使用 Pcap.net 进行 mDNS 查询？

Question

问题：我正在寻找一个 mDNS 数据包，同时在堆栈流中搜索选项。我尝试了 bonjour 和一些包装器，但成功非常有限，尤其是当我第二次请求并收到套接字绑定投诉时（当然，这可能是我的代码而不是它们）。

由于 VB.net 没有我所知道的真正可编辑的 dnsquery，我在 pcapdotnet 的构建 DNS 数据包中使用了 DNS 层，并且我自己一层一层地制作数据包。我认为这是一个不错的选择，但我对如何做到这一点有点迷茫。

这是我们想要的问题：

        q_name = new QuestionName("_axis-video._tcp.local"),
        q_type = QueryConstants.Question.QuestionType.PTR,
        q_class = QueryConstants.Question.QuestionClass.IN

这是我根据他们的标准编辑的 BuildDNSPacket 函数：

Private Shared Function BuildDnsPacket(destmac As String, domainName As String) As Packet

    'get source MAC address of PC
    Dim nic = System.Net.NetworkInformation.NetworkInterface.GetAllNetworkInterfaces()
    Dim source As String = nic(0).GetPhysicalAddress().ToString
    Dim sourcearray As Byte() = System.Text.Encoding.ASCII.GetBytes(source)

    'format
    Dim sourceMacStr As String = ""
    For i As Integer = 0 To sourcearray.Count - 1 Step 2
        sourceMacStr += Chr(sourcearray(i)) & Chr(sourcearray(i + 1)) & ":"
    Next

    ' Will be filled automatically.
    Dim ethernetLayer As New EthernetLayer() With { _
         .Source = New MacAddress(sourceMacStr.Substring(0, 17)), _
          .Destination = New MacAddress(destmac), _
          .EtherType = EthernetType.None _
    }

    ' Will be filled automatically.
    Dim ipV4Layer As New IpV4Layer() With { _
          .Source = New IpV4Address("1.2.3.4"), _
          .CurrentDestination = New IpV4Address(destmac), _
          .Fragmentation = IpV4Fragmentation.None, _
          .HeaderChecksum = Nothing, _
          .Identification = 123, _
          .Options = IpV4Options.None, _
          .Protocol = Nothing, _
          .Ttl = 100, _
          .TypeOfService = 0 _
    }

    ' Will be filled automatically.
    Dim udpLayer As New UdpLayer() With { _
          .SourcePort = 5353, _
          .DestinationPort = 5353, _
          .Checksum = Nothing, _
          .CalculateChecksumValue = False _
    }

    Dim dnsLayer As New DnsLayer() With { _
          .Id = 0, _
          .IsResponse = False, _
          .OpCode = DnsOpCode.Query, _
          .IsAuthoritativeAnswer = False, _
          .IsTruncated = False, _
          .IsRecursionDesired = False, _
          .IsRecursionAvailable = False, _
          .FutureUse = False, _
          .IsAuthenticData = False, _
          .IsCheckingDisabled = False, _
          .ResponseCode = DnsResponseCode.NoError, _
          .Queries = {New DnsQueryResourceRecord(New DnsDomainName(domainName), DnsType.Ptr, DnsClass.Any)}, _
          .Answers = Nothing, _
          .Authorities = Nothing, _
          .Additionals = Nothing, _
          .DomainNameCompressionMode = DnsDomainNameCompressionMode.All _
    }


    Dim builder As New PacketBuilder(ethernetLayer, ipV4Layer, udpLayer, dnsLayer)

    Return builder.Build(DateTime.Now)
End Function

主要区别是我将 DnsType 更改为 PTR 并将端口更改为 5353。

问题：我还应该添加或更改什么以使其成为 mDNS？我可以在域名中添加什么？我应该改变 dnsclass 吗？

绝对欢迎所有或任何建议。

Answer 1

我正在回答我的问题，以防其他需要在 vb.net 中执行 mDNS 的人需要这个：

解决方案：我不需要向 DNS 层添加任何东西来完成这项工作。我将 DNS 层更改为以下：

   Dim dnsLayer As New DnsLayer() With { _
          .Id = 0, _
          .IsResponse = False, _
          .OpCode = DnsOpCode.Query, _
          .IsAuthoritativeAnswer = False, _
          .IsTruncated = False, _
          .IsRecursionDesired = False, _
          .IsRecursionAvailable = False, _
          .FutureUse = False, _
          .IsAuthenticData = False, _
          .IsCheckingDisabled = False, _
          .ResponseCode = DnsResponseCode.NoError, _
          .Queries = {New DnsQueryResourceRecord(New DnsDomainName(domainName), DnsType.Ptr, DnsClass.Any)}, _
          .Answers = Nothing, _
          .Authorities = Nothing, _
          .Additionals = Nothing, _
          .DomainNameCompressionMode = DnsDomainNameCompressionMode.All _
    }

我把Ipv4层的输出地址设置为“224.0.0.251”的组播地址，将端口改为5353，使用上面列出的问题的域名。

这是一个显示响应的wireshark：